Process for sharpening the ends of fine wires.



ATEfi A Q.

PAUL FRIEDRICH, OF WENDENSCHLOSS, NEAR CUPENICK, GERMANY, ASSIGNOR TO JULIUS PINTSCH AKTIENGESELLSCHAFT, OF BERLIN, GERMANY.

PROCESS FOR SHARPENING TI-IE ENDS OF FINE WIRES.

No Drawing",

To all whom it may concern Be it known that I, PAUL FRIEDRICH, a citizen of the German Empire, and residing at Nendenschloss, near Copenick, German Empire, have invented certain new and useful Improvements in the Process forSharpening the Ends of Fine 'Wires, of which the following is a description.

In connection with the manufacture of metal filaments or incandescent lamps from highly refractory metals it is usual of late to impart to the same the desired elasticity and fineness by drawing them consecutively through a series of orifices of decreasing diameter. Thus wires of a certain diameter are drawn through orifices of a smaller diameter and consequently the ends of such wires or filaments must be pointed or sharpened in order to render it possible to introduce the same into the smaller orifice and to grip the end from the opposite side. lVith some of the metals employed for the manufacture of these filaments or wires, it is possible to sharpen or point the ends mechanically, this is however not possible with all very highly refractory metals, for 1nstance, with tungsten.

According to the process forming the ob ject of the present invention, the ends of the wire or filament are pointed or sharpened by means of oxidation.

If the end of the wire or filament, is heated, for instance, in a Bunsen flame of sufliciently high temperature, the surface of the same will oxidize and, on removing the residues of the oxidation, the diameter of the filament or wire will be correspondingly Specification of Letters Patent.

Application filed December 12, 1911.

Patented Mar. 1'7, 1914:.

Serial No. 665,247.

decreased according to the duration of the glowing period. The pointing or sharpening of the ends of the wire or filament is attained by gradually increasing the degree of oxidation toward the end of the wire or filament. The necessary temperature may be attained by means of the electric current. The decrease of diameter may also be effected at points in the length of the wire, which may then be divided at such points where the diameter is smallest, so that a length of wire having pointed ends will be attained. The oxidation may take place in air or in any suitable gas or substance containing oxygen.

I claim as my invention 1. A process for sharpening or producing points on the ends of metallic filaments of highly refractory metals, said process consisting in surrounding the end of the filament with a gas containing oxygen and applying heat to said end, whereby the filament is oxidized; and removing the oxidized portion.

2., A process for sharpening or producing points on the ends of metallic filaments of highly refractory metals, said process consisting in oxidizing the end of the filament by heating the end in a gas containing oxygen, and increasing the degree of oxidization toward the end of the filament.

In testimony whereof I afiix my signature in the presence of two witnesses.

PAUL FRIEDRICH.

Witnesses HENRY Hasrnn, VVOLDEMAR HAUPT.

Copies of this patent may be obtained for five cents each, by addressing the Gommleuioner of Patents, Washington, D. G. 

